ABSTRACT
Detection of BRAFV600E within cell free tumor DNA (ctDNA) is emerging as a promising means to improve patients' stratification or enable BRAF inhibitor (BRAFi) therapeutic monitoring in a minimally invasive manner. Here, we investigated whether extracellular vesicle-(EV)-associated-DNA (EV-DNA) has value as an alternative source of circulating BRAFV600E. To do so, we identified a clinical practice-compatible protocol for the isolation of EV-DNA and assessed BRAF gene status on plasma samples from metastatic melanoma patients at the beginning and during BRAFi therapy. This protocol uses a peptide with high affinity for EVs and it has been found to recover more mutant DNA from plasma than standard ultracentrifugation. Molecular analyses revealed that mutant DNA is largely unprotected from nuclease digestion, interacting with the outer side of the EV membrane or directly with the peptide. When used on clinical samples, we found that the protocol improves the detection of BRAFV600E gene copies in comparison to the reference protocol for ctDNA isolation. Taken together, these findings indicate that EVs are a promising source of mutant DNA and should be considered for the development of next-generation liquid biopsy approaches.
Subject(s)
Exosomes/genetics , Melanoma/drug therapy , Nivolumab/therapeutic use , Proto-Oncogene Proteins B-raf/genetics , Aged , Cell Line, Tumor , Circulating Tumor DNA , Female , Humans , Male , Melanoma/blood , Melanoma/genetics , Mutation , Neoplasm MetastasisABSTRACT
AIM: A survival benefit was demonstrated by dabrafenib + trametinib for metastatic BRAF-mutated melanoma patients. Best response is a strong prognostic marker for survival. PATIENTS & METHODS: The specific features associated with complete response (CR) were evaluated. RESULTS: A total of 15/66 patients achieved CR. Median size of lesions was 3 cm (range: 0.5-10). Using that value as cut-off, the CR rate was 39.3% in patients with smaller lesions and 10.5% in patients with bigger size (p = 0.006). The clinical features associated with CR were the number of metastatic sites and the largest diameter of the biggest metastatic site. CONCLUSION: The number of the metastases and the diameter of the largest metastatic site are associated with a higher CR rate.
